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Energy Evolution Characteristics of Sandstones During Confining Pressure Cyclic Unloading Conditions
Abstract Periodical cyclic loads are often sustained in actual engineering. In this paper, the mechanical properties, energy density parameters characteristics and energy evolution patterns of sandstone under confining pressure cyclic loading and unloading (CCLU) conditions are investigated. The results show that the elastic modulus and Poisson’s ratio of the samples significantly increase with initial confining pressures, and decrease gradiently in the entire CCLU test. It is thus well illustrated that the stress state can be improved under the high confining pressure, which enhances the resistance to further micro-cracks extension, and has a certain inhibition effect on the strain. Then, the elastic energy density ratio (EEDR) is far higher than that of the dissipated energy density ratio (DEDR), most of the energy absorbed by the rock is converted into elastic energy. The decrease in EEDR and the increase of DEDR are the precursors of rock sample failure, and the dissipated energy reflects the attenuation degree of the rock's initial strength. The axial (radial) energy density of the rock has a prominent nonlinear relationship with confining pressure, it satisfies the characteristics of the quadratic curve. Furthermore, the energy calculation method adopted in this paper is not only suitable for the pressure relief condition of rock, but also for the complicated unloading path of rock under the action of excavation disturbance. Research on the nonlinear mechanical characteristics and energy storage and release law of the rock under CCLU is helpful to understanding the failure mechanism of rock mass, and then scientifically researching the dynamic disasters, such as rockburst and percussive ground pressure.
Highlights Energy evolution characteristics of sandstone under cyclic unloading stress conditions are elaborated based on the deformation characteristics. Reveal the characteristics and behaviors under different confining pressures, such as energy conversion, unloading deformation, and failure characteristics.The total energy density and elastic energy density of the rock show a nonlinear decline with the characteristics of the quadratic curve. The decrease of elastic energy ratio and the increase of dissipated energy ratio are the precursors of rock sample failure. The dissipated energy ratio increases nonlinearly with the unloading confining pressure.The reasons for the energy evolution characteristics under complex stress paths at different stages are explained. Results indicate that the energy calculation method adopted in this paper is not only suitable for the pressure relief condition of rock, but also for the complicated unloading path of rock under the action of excavation disturbance.
Energy Evolution Characteristics of Sandstones During Confining Pressure Cyclic Unloading Conditions
Abstract Periodical cyclic loads are often sustained in actual engineering. In this paper, the mechanical properties, energy density parameters characteristics and energy evolution patterns of sandstone under confining pressure cyclic loading and unloading (CCLU) conditions are investigated. The results show that the elastic modulus and Poisson’s ratio of the samples significantly increase with initial confining pressures, and decrease gradiently in the entire CCLU test. It is thus well illustrated that the stress state can be improved under the high confining pressure, which enhances the resistance to further micro-cracks extension, and has a certain inhibition effect on the strain. Then, the elastic energy density ratio (EEDR) is far higher than that of the dissipated energy density ratio (DEDR), most of the energy absorbed by the rock is converted into elastic energy. The decrease in EEDR and the increase of DEDR are the precursors of rock sample failure, and the dissipated energy reflects the attenuation degree of the rock's initial strength. The axial (radial) energy density of the rock has a prominent nonlinear relationship with confining pressure, it satisfies the characteristics of the quadratic curve. Furthermore, the energy calculation method adopted in this paper is not only suitable for the pressure relief condition of rock, but also for the complicated unloading path of rock under the action of excavation disturbance. Research on the nonlinear mechanical characteristics and energy storage and release law of the rock under CCLU is helpful to understanding the failure mechanism of rock mass, and then scientifically researching the dynamic disasters, such as rockburst and percussive ground pressure.
Highlights Energy evolution characteristics of sandstone under cyclic unloading stress conditions are elaborated based on the deformation characteristics. Reveal the characteristics and behaviors under different confining pressures, such as energy conversion, unloading deformation, and failure characteristics.The total energy density and elastic energy density of the rock show a nonlinear decline with the characteristics of the quadratic curve. The decrease of elastic energy ratio and the increase of dissipated energy ratio are the precursors of rock sample failure. The dissipated energy ratio increases nonlinearly with the unloading confining pressure.The reasons for the energy evolution characteristics under complex stress paths at different stages are explained. Results indicate that the energy calculation method adopted in this paper is not only suitable for the pressure relief condition of rock, but also for the complicated unloading path of rock under the action of excavation disturbance.
Energy Evolution Characteristics of Sandstones During Confining Pressure Cyclic Unloading Conditions
Zhao, Yu (author) / Dang, Shuang (author) / Bi, Jing (author) / Wang, Chaolin (author) / Gan, Fei (author) / Li, Jiashen (author)
2022
Article (Journal)
Electronic Resource
English
BKL:
38.58
Geomechanik
/
56.20
Ingenieurgeologie, Bodenmechanik
/
38.58$jGeomechanik
/
56.20$jIngenieurgeologie$jBodenmechanik
RVK:
ELIB41
Energy Evolution and Brittleness Analysis of Sandstone Under Confining Pressure Unloading
| Springer Verlag | 2024